A transparent display device is a display apparatus in which a background behind can be seen, and the transparent display device was primarily realized by projecting an image on a non-emissive liquid crystal panel. However, there has been currently developed a display apparatus that directly includes a transparent display device. As a liquid-crystal display (LCD) has an excellent shading ratio but uses two polarizing plates, the liquid-crystal display has low transmittance, thus it is difficult to be used as a transparent display device. Especially, the transparent display device is mostly realized by an organic light-emitting display (OLED) device capable of self-emitting. Such a transparent display device is applied to a front glass of a vehicle or a glass for home to provide a user with information on the display device and information of an ambient environment at the same time.